Change Caching Policy

[taooceros]

Change Cache to Concurrentlfu in BitFaster.Caching. The eviction policy seems to be undesirable for our cases.

neon-sunset/fast-cache#107

Changes:

• Remove the usage property in the cache, since we are not managing the cache ourselves.

Tested:

• With a relatively small cache size, the icon is not flickering when type continuous query that consistently get the same result. (like "vscode" or "powerpoint").

[onesounds]

After changing maxcached, I noticed that when I return after keystrokes and context menu switching, the icons are not flickering and display well.